Regulation of intracellular activities by a variety of extracellular signals often involves cell-surface receptors which interact with guanine nucleotide-binding regulatory proteins (G-proteins). It is generally known that G-proteins regulate other proteins, yet little is known about the regulation of the expression of G-proteins themselves. The purpose of this project is to investigate how the levels of G-protein expression may be regulated in select preleukemic (K562, U937, and HL-60) cell lines, and whether altered levels of specific G-protein subunits correlate with physiologic end-points such as cell growth, proliferation, or differentiation. This correlation could provide insight on defining the molecular mechanisms underlying changes in cellular concentrations of G-protein subunits. Western immunoblotting will be used to identify both the types and relative amounts of G-proteins expressed in K562, U937, and HL-6O hematopoietic cells. Northern blotting, western immunoblotting, nuclear run-on assays, and other molecular techniques will be performed to establish which G-proteins and their transcripts are expressed as different growth conditions are imposed on the cells.